This disclosure relates generally to light-off of a turbomachine combustor and, more particularly, to increasing fuel delivery to a turbomachine combustor until achieving light-off.
Turbomachines transfer energy from a rotor to a fluid as is known. During operation, air is pulled into the turbomachine. In a gas turbine machine the air is then compressed, mixed with fuel and combusted. The products of combustion expand to rotatably drive a turbine section of the turbomachine.
A fuel system delivers fuel to a combustor of the turbomachine during a typical startup. An igniter is then activated to light the fuel. Light-off is the point at which the delivered fuel ignites. To achieve light-off, the fuel must be delivered to the combustor at the appropriate rate. Many fuel systems include complex and costly arrangements of pressure sensors and metering valves to ensure that the fuel system delivers fuel to the combustor at rate appropriate to achieve light-off. These components attempt to compensate, for example, for differences between a desired fuel delivery rate and an actual fuel delivery rate. Differences may occur due to production tolerances, fuel types, temperatures, altitude conditions, etc.
One example turbomachine is an auxiliary power unit (APU). A typical APU is located in the tail section of a large aircraft. The APU typically provides power (electrical, hydraulic, or shaft), and compressed air to the aircraft.